New oxindole-bridged acceptors for organic sensitizers: Substitution and performance studies in dye-sensitized solar cells

New D-π-A configured organic sensitizers featuring halogen-substituted oxindole-bridged acceptor units have been synthesized for dye-sensitized solar cells applications. Among fluorine, bromine, and iodine substitution, the cell based on bromine incorporated dye exhibited the highest efficiency. The oxindoles in these sensitizers were found to assist the electron injection through the chelation of their amide carbonyl groups to the TiO₂ surface. This study provides an alternate approach for future rational dye design to gain excellent DSSC performance.